<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script src="../vue.js"></script>
</head>

<body>

  <div id="app">
    <button @click="decrement(2,$event)">-</button>
    <h1>{{count}}</h1>
    <button @click="increment(3)">+</button>
  </div>



  <script>

    var vm = new Vue({
      el: '#app',
      data: {
        count: 0
      },
      methods: {
        increment(num) {
          this.count += num;
        },
        decrement(num, evt) {
          this.count -= num;
          console.log(evt.target)
        }
      }
    })

  </script>

</body>

</html>